noble gas | Definition, Properties, Uses, & Facts | Britannica.com neon (Ne) Noble gas, any of the seven chemical elements that make up Group 18 (VIIIa) of the periodic table . The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and oganesson (Og). The noble gases are colourless, odourless, tasteless, nonflammable gases . They traditionally have been labeled Group 0 in the periodic table because for decades after their discovery it was believed that they could not bond to other atoms ; that is, that their atoms could not combine with those of other elements to form chemical compounds . Their electronic structures and the finding that some of them do indeed form compounds has led to the more appropriate designation , Group 18. When the members of the group were discovered and identified, they were thought to be exceedingly rare, as well as chemically inert, and therefore were called the rare or inert gases. It is now known, however, that several of these elements are quite abundant on Earth and in the rest of the universe , so the designation rare is misleading.

Similarly, use of the term inert has the drawback that it connotes chemical passivity, suggesting that compounds of Group 18 cannot be formed. In chemistry and alchemy , the word noble has long signified the reluctance of metals , such as gold and platinum , to undergo chemical reaction ; it applies in the same sense to the group of gases covered here. The abundances of the noble gases decrease as their atomic numbers increase. Helium is the most plentiful element in the universe except hydrogen . All the noble gases are present in Earth’s atmosphere and, except for helium and radon, their major commercial source is the air , from which they are obtained by liquefaction and fractional distillation . Most helium is produced commercially from certain natural gas wells. Radon usually is isolated as a product of the radioactive decomposition of radium compounds. The nuclei of radium atoms spontaneously decay by emitting energy and particles, helium nuclei ( alpha particles ) and radon atoms. Some properties of the noble gases helium polonium (Po) In 1785 Henry Cavendish , an English chemist and physicist, found that air contains a small proportion (slightly less than 1 percent) of a substance that is chemically less active than nitrogen .

A century later Lord Rayleigh , an English physicist, isolated from the air a gas that he thought was pure nitrogen, but he found that it was denser than nitrogen that had been prepared by liberating it from its compounds. He reasoned that his aerial nitrogen must contain a small amount of a denser gas. In 1894, Sir William Ramsay , a Scottish chemist, collaborated with Rayleigh in isolating this gas, which proved to be a new element— argon . Apparatus used in the isolation of argon by English physicist Lord Rayleigh and chemist Sir William … Encyclopædia Britannica, Inc. After the discovery of argon, and at the instigation of other scientists, in 1895 Ramsay investigated the gas released upon heating the mineral clevite, which was thought to be a source of argon. Instead, the gas was helium , which in 1868 had been detected spectroscopically in the Sun but had not been found on Earth . Ramsay and his coworkers searched for related gases and by fractional distillation of liquid air discovered krypton , neon , and xenon , all in 1898.

Radon was first identified in 1900 by German chemist Friedrich E. Dorn; it was established as a member of the noble-gas group in 1904. Rayleigh and Ramsay won Nobel Prizes in 1904 for their work. In 1895 the French chemist Henri Moissan , who discovered elemental fluorine in 1886 and was awarded a Nobel Prize in 1906 for that discovery, failed in an attempt to bring about a reaction between fluorine and argon. This result was significant because fluorine is the most reactive element in the periodic table. In fact, all late 19th- and early 20th-century efforts to prepare chemical compounds of argon failed. The lack of chemical reactivity implied by these failures was of significance in the development of theories of atomic structure. In 1913 the Danish physicist Niels Bohr proposed that the electrons in atoms are arranged in successive shells having characteristic energies and capacities and that the capacities of the shells for electrons determine the numbers of elements in the rows of the periodic table.

On the basis of experimental evidence relating chemical properties to electron distributions, it was suggested that in the atoms of the noble gases heavier than helium, the electrons are arranged in these shells in such a way that the outermost shell always contains eight electrons, no matter how many others (in the case of radon, 78 others) are arranged within the inner shells. Britannica Stories Ringling Bros. Folds Its Tent In a theory of chemical bonding advanced by American chemist Gilbert N. Lewis and German chemist Walther Kossel in 1916, this octet of electrons was taken to be the most stable arrangement for the outermost shell of any atom. Although only the noble-gas atoms possessed this arrangement, it was the condition toward which the atoms of all other elements tended in their chemical bonding. Certain elements satisfied this tendency by either gaining or losing electrons outright, thereby becoming ions ; other elements shared electrons, forming stable combinations linked together by covalent bonds . The proportions in which atoms of elements combined to form ionic or covalent compounds (their “ valences ”) were thus controlled by the behaviour of their outermost electrons, which—for this reason—were called valence electrons .

This theory explained the chemical bonding of the reactive elements, as well as the noble gases’ relative inactivity, which came to be regarded as their chief chemical characteristic. (See also chemical bonding: Bonds between atoms .) Shell atomic model Periodic Table of the Elements Screened from the nucleus by intervening electrons, the outer (valence) electrons of the atoms of the heavier noble gases are held less firmly and can be removed (ionized) more easily from the atoms than can the electrons of the lighter noble gases. The energy required for the removal of one electron is called the first ionization energy . In 1962, while working at the University of British Columbia , British chemist Neil Bartlett discovered that platinum hexafluoride would remove an electron from (oxidize) molecular oxygen to form the salt [O2+][PtF6−]. The first ionization energy of xenon is very close to that of oxygen; thus Bartlett thought that a salt of xenon might be formed similarly. In the same year, Bartlett established that it is indeed possible to remove electrons from xenon by chemical means.

He showed that the interaction of PtF6 vapour in the presence of xenon gas at room temperature produced a yellow-orange solid compound then formulated as [Xe+][PtF6−]. (This compound is now known to be a mixture of [XeF+][PtF6−], [XeF+] [Pt2F11−], and PtF5.) Shortly after the initial report of this discovery, two other teams of chemists independently prepared and subsequently reported fluorides of xenon—namely, XeF2 and XeF4. These achievements were soon followed by the preparation of other xenon compounds and of the fluorides of radon (1962) and krypton (1963). Connect with Britannica Facebook Twitter YouTube Instagram Pinterest In 2006, scientists at the Joint Institute for Nuclear Research in Dubna , Russia , announced that oganesson , the next noble gas, had been made in 2002 and 2005 in a cyclotron .

(Most elements with atomic numbers greater than 92—i.e., the transuranium elements —have to be made in particle accelerators.) No physical or chemical properties of oganesson can be directly determined since only a few atoms of oganesson have been produced. General properties of the group Each noble-gas element is situated in the periodic table between an element of the most electronegative group, the halogen elements (Group 17, the atoms of which add electrons to achieve the octet and thereby become negative ions ), and an element of the most electropositive group, the alkali metals (Group 1, the atoms of which lose electrons to become positive ions). Several important uses of the noble gases depend on their reluctance to react chemically. Their indifference toward oxygen , for example, confers utter nonflammability upon the noble gases. Although helium is not quite as buoyant as hydrogen , its incombustibility makes it a safer lifting gas for lighter-than-air craft.

The noble gases—most often helium and argon , the least expensive—are used to provide chemically unreactive environments for such operations as cutting, welding , and refining of metals such as aluminum (atmospheric oxygen and, in some cases, nitrogen or carbon dioxide would react with the hot metal). The helium-filled balloon Bubble, manned by a scientist … James Aldred/Nature Picture Library Editor Picks: Exploring 10 Types of Basketball Movies The noble gases absorb and emit electromagnetic radiation in a much less complex way than do other substances. This behaviour is used in discharge lamps and fluorescent lighting devices: if any noble gas is confined at low pressure in a glass tube and an electrical discharge is passed through it, the gas will glow. Neon produces the familiar orange-red colour of advertising signs; xenon emits a beautiful blue colour. Neon signs along Nanking Road, Shanghai. Paul Souders/Corbis Noble gases have uses that are derived from their other chemical properties. The very low boiling points and melting points of the noble gases make them useful in the study of matter at extremely low temperatures .

The low solubility of helium in fluids leads to its admixture with oxygen for breathing by deep-sea divers : because helium does not dissolve in the blood , it does not form bubbles upon decompression (as nitrogen does, leading to the condition known as decompression sickness , or the bends ). Xenon has been used as an anesthetic ; although it is costly, it is nonflammable and readily eliminated from the body. Radon is highly radioactive ; its only uses have been those that exploit this property (e.g., radiation therapy ). (Oganesson is also radioactive, but, since only a few atoms of this element have thus far been observed, its physical and chemical properties cannot be documented.) Only krypton , xenon, and radon are known to form stable compounds. The compounds of these noble gases are powerful oxidizing agents (substances that tend to remove electrons from others) and have potential value as reagents in the synthesis of other chemical compounds . noble gases - Student Encyclopedia (Ages 11 and up) Six elemental gases are composed of such exceptionally stable atoms that they almost never react with other elements.

They are the gases that make up Group 0 (the rightmost column) of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). When they were first discovered, these gases were thought to be exceedingly rare and completely inactive; thus they were named the rare gases, inert gases, or noble gases (the term noble, in chemistry and alchemy, had long signified a lack of chemical reactivity). Article Contributors Atomic number 86 - definition of atomic number 86 by The Free Dictionary Atomic number 86 - definition of atomic number 86 by The Free Dictionary Also found in: Thesaurus , Wikipedia . Related to atomic number 86: mass number ThesaurusAntonymsRelated WordsSynonymsLegend: Noun 1.

atomic number 86 - a radioactive gaseous element formed by the disintegration of radium; the heaviest of the inert gasses; occurs naturally (especially in areas over granite) and is considered a hazard to health radon , Rn chemical element , element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter argonon , inert gas , noble gas - any of the chemically inert gaseous elements of the helium group in the periodic table Want to thank TFD for its existence? Tell a friend about us , add a link to this page, or visit the webmaster's page for free fun content . Link to this page: Copyright © 2003-2017 Farlex, Inc Disclaimer All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.

The Noble Gases (Group 18) About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. The Noble Gases (Group 18) Noble gases are the six chemical elements of Group 18 of the periodic table, being monatomic and (with very limited exceptions) inert. Learning Objective Identify the properties of the noble gases. Key Points Noble gases are colorless, odorless, tasteless, and nonflammable gases under standard conditions. In the periodic table, the noble gases are arranged according to their boiling point . Noble gases are widely used in different fields, from incandescent lighting to excimer lasers. Xenon is used as an anesthetic because of its high solubility in lipids, which makes it more potent than the usual nitrous oxide , and because it is readily eliminated from the body, which allows for faster recovery.

Xenon finds application in medical imaging of the lungs through hyperpolarized MRI . Radon, which is highly radioactive and is only available in minute amounts, is used in radiotherapy. Terms Register for FREE to remove ads and unlock more features! Learn more Full Text The noble gases are a group of chemical elements that make up Group 18 on the periodic table. These gases all have similar properties under standard conditions: they are all odorless, colorless, monatomic gases with very low chemical reactivity . The six noble gases that occur naturally are helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). Properties of the Noble Gases The properties of the noble gases can be well explained by modern theories of atomic structure. The outer shell of valence electrons is considered to be "full" in noble gases, giving them little tendency to participate in chemical reactions . It has been possible to prepare only a few hundred noble gas compounds . In the case of Neon (Ne), for example, both the n = 1 and n = 2 shells are complete and therefore it is a stable monatomic gas under ambient conditions.

The noble gases have weak interatomic forces and consequently have very low melting and boiling points. They are all monatomic gases under standard conditions, including those with larger atomic masses than many other elements that are solids under standard conditions. Electron Configurations in the Noble Gases The noble gas atoms , as do the atoms in most other groups on the periodic table, increase steadily in atomic radius from one period to the next due to an increasing number of electrons. The size of the atom is related to several properties. For example, the ionization potential decreases with an increasing radius because the valence electrons in the larger noble gases are farther away from the nucleus and so are not held as tightly together by the atom. Noble gases have the largest ionization potential among the elements of each period. This reflects the stability of their electron configuration and points again to their relative lack of chemical reactivity. Inert Gases The noble gases were originally also referred to as "inert gases," since it was believed that they did not react with other elements to form compounds. In recent years, however, this term has fallen out of favor, although you will occasionally see it in older literature.

Scientists have discovered that, since the heavier noble gas atoms are held together less strongly by electromagnetic forces than are the lighter noble gases, such as helium, the outer electrons of these heavier atoms can be removed more easily. Because of this, many compounds of the gases xenon, krypton, and radon can, in fact, be formed. Of the six noble gases, only krypton, xenon, and radon have the ability to form stable compounds. These are used as oxidizing agents . Applications for the Noble Gases The noble gases glow in distinctive colors when used inside gas-discharge lamps, such as neon lights. Xenon is commonly used in xenon arc lamps, which are present in film projectors and automobile headlights due to their nearly continuous spectrum that resembles daylight. Under the correct conditions, brightly lit and colorful signs can be made using noble gases. "Neon Lights" is the common term, but any of the noble gases can be used. The noble gases are also used in excimer lasers, which are based on short-lived electronically excited molecules known as excimers.

The excimers used for lasers may be noble gas dimers such as Ar2, Kr2, or Xe2, or, more commonly, the noble gas is combined with a halogen in excimers such as ArF, KrF, XeF, or XeCl. These lasers produce ultraviolet light, which, due to its short wavelength (193 nm for ArF and 248 nm for KrF), allows for high-precision imaging. Excimer lasers have many industrial, medical, and scientific applications. They are used for microlithography and microfabrication, which are essential for integrated circuit manufacturing; and for laser surgery, including laser angioplasty and eye surgery. What does atomic number 86 mean?

definition and meaning (Free English Language Dictionary) atomic number 86; radon ; Rn Hypernyms ("atomic number 86" is a kind of...): chemical element ; element (any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter) argonon ; inert gas ; noble gas (any of the chemically inert gaseous elements of the helium group in the periodic table) Learn English with...

Proverbs of the week "Cowards die many times, but a brave man only dies once." (English proverb) "We do not inherit the world from our ancestors; we borrow it from our children." (Native American proverb, tribe unknown) "Write the bad things that are done to you in sand, but write the good things that happen to you on a piece of marble." (Arabic proverb) "Knowledge is in the head, not the copybook." (Egyptian proverb) ATOMIC NUMBER 86: related words searches Noble Gases: An Element Family Noble Gases: An Element Family Noble Gases: A Chemical Family By, Location on the Periodic Table 4 Created with CAST's UDL Book Builder This book is all about the farthest right column of the Periodic Table: the Noble Gases. The elements that classify as Noble Gases are Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). As their name implies, they are all gases at room temperature. The Noble Gases are special because their outer shell has the maximum number of electrons allowed in it. Because of this, they are mostly unreactive.

You may see the Noble Gases be refered to as the "Inert Gases." The word "inert' means "inactive." Created with CAST's UDL Book Builder The Noble Gases are located in the column the farthest to the right on the Periodic Table. This is also called Group 8A, 18 or even Group Zero! With the exception of Helium which has 2, all of the Noble Gases have eight valence electrons. This means they would not have to gain or lose any electrons to become stable because they already are, so their valence number would be zero. Lastly, if you go across the Periodic Table counting each column, the Noble Gases would be the 18th one you count. Created with CAST's UDL Book Builder Since atomic radius decreases from left to right, and the Noble Gases are farthest to the right, they have a low atmoic radius. As you go down the family, the atomic radius increases. The Noble Gas with the highest atomic radius would be Radon. Created with CAST's UDL Book Builder Ionization energy is the amount of energy required to remove the most loosely held electron.

Since Noble Gases have a full outer shell, it would take a lot of energy to rip an electron from it. Noble Gases have high ionization energy, and Helium has the highest ionization energy. Created with CAST's UDL Book Builder Electronegativity is the ability of an element to gain an electron in a bonding situation. As mentioned earlier, Noble Gases already have a full octet, so they don't need to attract any more electrons. Therefore, Noble Gases don't have electronegativity either! Noble gases facts, information, pictures | Encyclopedia.com articles about Noble gases Isolation of the Noble Gases HELIUM. Helium is an unusual element in many respects—not least because it is the only element to have first been identified in the Solar System before it was discovered on Earth.

This is significant, because the elements on Earth are the same as those found in space: thus, it is more than just an attempt at sounding poetic when scientists say that humans, as well as the world around them, are made from "the stuff of stars." In 1868, a French astronomer named Pierre Janssen (1824-1907) was in India to observe a total solar eclipse. To aid him in his observations, he used a spectroscope, an instrument for analyzing the spectrum of light emitted by an object. What Janssen's spectroscope showed was surprising: a yellow line in the spectrum, never seen before, which seemed to indicate the presence of a previously undiscovered element. Janssen called it "helium" after the Greek god Helios, or Apollo, whom the ancients associated with the Sun . Janssen shared his findings with English astronomer Sir Joseph Lockyer (1836-1920), who had a worldwide reputation for his work in analyzing light waves. Lockyer, too, believed that what Janssen had seen was a new element, and a few months later, he observed the same unusual spectral lines.

At that time, the spectroscope was still a new invention, and many members of the worldwide scientific community doubted its usefulness, and therefore, in spite of Lockyer's reputation, they questioned the existence of this "new" element. Yet during their lifetimes, Janssen and Lockyer were proven correct. NEON, ARGON, KRYPTON, AND XENON. They had to wait a quarter century, however. In 1893, English chemist Sir William Ramsay (1852-1916) became intrigued by the presence of a mysterious gas bubble left over when nitrogen from the atmosphere was combined with oxygen. This was a phenomenon that had also been noted by English physicist Henry Cavendish (1731-1810) more than a century before, but Cavendish could offer no explanation. Ramsay, on the other hand, had the benefit of observations made by English physicist John William Strutt, Lord Rayleigh (1842-1919). Up to that time, scientists believed that air consisted only of oxygen, carbon dioxide, and water vapor.

However, Rayleigh had noticed that when nitrogen was extracted from air after a process of removing those other components, it had a slightly higher density than nitrogen prepared from a chemical reaction. In light of his own observations, Ramsay concluded that whereas nitrogen obtained from chemical reactions was pure, the nitrogen extracted from air contained trace amounts of an unknown gas. Ramsay was wrong in only one respect: hidden with the nitrogen was not one gas, but five. In order to isolate these gases, Ramsay and Rayleigh subjected air to a combination of high pressure and low temperature, allowing the various gases to boil off at different temperatures. One of the gases was helium—the first confirmation that the element existed on Earth—but the other four gases were previously unknown. The Greek roots of the names given to the four gases reflected scientists' wonder at discovering these hard-to-find elements: neos (new), argos (in active), kryptos (hidden), and xenon (stranger). RADON.

Inspired by the studies of Polish-French physicist and chemist Marie Curie (1867-1934) regarding the element radium and the phenomenon of radioactivity (she discovered the element, and coined the latter term), German physicist Friedrich Dorn (1848-1916) became fascinated with radium. Studying the element, he discovered that it emitted a radioactive gas, which he dubbed "radium emanation." Eventually, however, he realized that what was being produced was a new element. This was the first clear proof that one element could become another through the process of radioactive decay. Ramsay, who along with Rayleigh had received the Nobel Prize in 1904 for his work on the noble gases, was able to map the new element's spectral lines and determine its density and atomic mass. A few years later, in 1918, another scientist named C. Schmidt gave it the name "radon." Due to its behavior and the configuration of its electrons, chemists classified radon among what they continued to call the "inert gases" for another half-century—until Bartlett's preparation of xenon compounds in 1962.

Presence of the Rare Gases on Earth IN THE ATMOSPHERE. Though the rare gases are found in minerals and meteorites on Earth, their greatest presence is in the planet's atmosphere. It is believed that they were released into the air long ago as a by-product of decay on the part of radioactive materials in the Earth's crust. Within the atmosphere, argon is the most "abundant"—in comparative terms, given the fact that the "rare gases" are, by definition, rare. Nitrogen makes up about 78% of Earth's atmosphere and oxygen 21%, meaning that these two elements constitute fully 99% of the air above the Earth. Argon ranks a distant third, with 0.93%. The remaining 0.07% is made up on water vapor, carbon dioxide, ozone (O3), and traces of the noble gases. These are present in such small quantities that the figures for them are not typically presented as percentages, but rather in terms of parts per million (ppm). The concentrations of neon, helium, krypton, and xenon in the atmosphere are 18, 5, 1, and 0.09 ppm respectively. IN THE SOIL.

Radon in the atmosphere is virtually negligible, which is a fortunate thing, in light of its radioactive qualities. Few Americans, in fact, even knew of its existence until 1988, when the United States Environmental Protection Agency (EPA) released a report estimating that some ten million American homes had potentially harmful radon levels. This set off a scare, and during the late 1980s and 1990s, sales of home radon detectors boomed. Meanwhile, the federal government increased concerns with additional reports, advising people to seal their basements and ventilate their homes if radon exceeded certain levels. A number of scientists have disputed the government's claims, yet some regions of the United States appear to be at relatively high risk due to the presence of radon in the soil. The element seems to be most plentiful in soils containing high concentrations of uranium. If radon is present in a home that has been weather-sealed to improve the efficiency of heating and cooling systems, it is indeed potentially dangerous to the residents. Chinese scientists in the 1960s made an interesting discovery regarding radon and its application to seismography, or the area of the earth sciences devoted to studying and predicting earthquakes.

Radon levels in groundwater, the Chinese reports showed, rise considerably just before an earthquake. Since then, the Chinese have monitored radon concentrations in water, and used this data to predict earthquakes. EXTRACTING RARE GASES. Radon, in fact, is not the only rare gas that can be obtained as the result of radioactive decay: in 1903, Ramsay and British chemist Frederick Soddy (1877-1956) showed that the breakdown of either uranium or radium results in the production of helium atoms (beta particles). A few years later, English physicist Ernest Rutherford (1871-1937) demonstrated that radiation carrying a positive electrical charge (alpha rays) was actually a stream of helium atoms stripped of an electron. Many of the noble gases are extracted by liquefying air—that is, by reducing it to temperatures at which it assumes the properties of a liquid rather than a gas. By controlling temperatures in the liquefied air, it is possible to reach the boiling point for a particular noble gas and thereby extract it, much as was done when these gases were first isolated in the 1890s. THE UNIQUE SITUATION OF HELIUM.

Helium is remarkable, in that it only liquefies at a temperature of −457.6°F (−272°C), just above absolute zero. Absolute zero is the temperature at which the motion of atoms or molecules comes to a virtual stop, but the motion of helium atoms never completely ceases. In order to liquefy it, in fact, even at those low temperatures, it must be subjected to pressures many times that exerted by Earth's atmosphere. Given these facts, it is difficult to extract helium from air. More often, it is obtained from natural gas wells, where it is present in relatively large concentrations—between 1% and 7% of the natural gas. The majority of the Earth's helium supply belongs to the United States, where the greatest abundance of helium-supplying wells are in Texas , Oklahoma , and Kansas . During World War II , the United States took advantage of this supply of relatively inexpensive helium to provide buoyancy for a fleet of airships used for reconnaissance. There is one place with an abundant supply of helium, but there are no plans for a mining expedition any time soon. That place is the Sun, where the nuclear fusion of hydrogen atoms creates helium.

Indeed, helium seems to be the most plentiful element of all, after hydrogen, constituting 23% of the total mass of the universe. Why, then, is it so difficult to obtain on Earth? Most likely because it is so light in comparison to air; it simply floats off into space. Applications for the Noble Gases RADON, ARGON, KRYPTON, AND XENON. Though radon is known primarily for the hazards it poses to human life and well-being, it has useful applications. As noted above, its presence in groundwater appears to provide a possible means of predicting earthquakes. In addition, it is used for detecting leaks, measuring flow rates, and inspecting metal welds. One interesting use of argon and, in particular, the stable isotope argon-40, is in dating techniques used by geologists, paleontologists, and other scientists studying the distant past. When volcanic rocks are subjected to extremely high temperatures, they release argon, and as the rocks cool, argon-40 accumulates.

Because argon-40 is formed by the radioactive decay of a potassium isotope, potassium-40, the amount of argon-40 that forms is proportional to the rate of decay for potassium-40. The latter has a half-life of 1.3 billion years, meaning that it takes 1.3 billion years for half the potassium-40 originally present to be converted to argon-40. Using argon-40, paleontologists have been able to estimate the age of volcanic layers above and below fossil and artifact remains in east Africa. Krypton has a number of specialized applications—for instance, it is mixed with argon and used in the manufacture of windows with a high level of thermal efficiency. Used in lasers, it is often mixed with a halogen such as fluorine. In addition, it is also sometimes used in halogen sealed-beam headlights. Many fans of Superman, no doubt, were disappointed at some point in their lives to discover that there is no such thing as "kryptonite," the fictional element that caused the Man of Steel to lose his legendary strength. Yet krypton—the real thing—has applications that are literally out of this world.

In the development of fuel for space exploration, krypton is in competition with its sister element, xenon. Xenon offers better performance, but costs about ten times more to produce; thus krypton has become more attractive as a fuel for space flight. In addition to its potential as a space fuel, xenon is used in arc lamps for motion-picture film projection, in high-pressure ultraviolet radiation lamps, and in specialized flashbulbs used by photographers. One particular isotope of xenon is utilized for tracing the movement of sands along a coastline. Xenon is also applied in high-energy physics for detecting nuclear radiation in bubble chambers. Furthermore, neuroscientists are experimenting with the use of xenon in diagnostic procedures to clarify x-ray images of the human brain. NEON. Neon, of course, is best-known for its application in neon signs, which produce an eye-catching glow when lit up at night. French chemist Georges Claude (1870-1960), intrigued by Ramsay's discovery of neon, conducted experiments that led to the development of the neon light in 1910. That first neon light was simply a glass tube filled with neon gas, which glowed a bright red when charged with electricity.

Claude eventually discovered that mixing other gases with neon produced different colors of light. He also experimented with variations in the shapes of glass tubes to create letters and pictures. By the 1920s, neon light had come into vogue, and it is still popular today. Modern neon lamps are typically made of plastic rather than glass, and the range of colors is much greater than in Claude's day: not only the gas filling, but the coating inside the tube, is varied, resulting in a variety of colors from across the spectrum. Though the neon sign is its best-known application, neon is used for many other things. Neon glow lamps are often used to indicate on/off settings on electronic instrument panels, and lightweight neon lamps are found on machines ranging from computers to voltage regulators. In fact, the first practical color television, produced in 1928, used a neon tube to produce the red color in the receiver. Green came from mercury, but the blue light in that early color TV came from another noble gas, helium. HELIUM. Helium, of course, is widely known for its use in balloons—both for large airships and for the balloons that have provided joy and fun to many a small child.

Though helium is much more expensive than hydrogen as a means of providing buoyancy to airships, hydrogen is extremely flammable, and after the infamous explosion of the airship Hindenburg in 1937, helium became the preferred medium for airships. As noted earlier, the United States military made extensive use of helium-filled airships during the World War II. The use of helium for buoyancy is one of the most prominent applications of this noble gas, but far from the only one. In fact, not only have people used helium to go up in balloons, but divers use helium for going down beneath the surface of the ocean. In that situation, of course, helium is not used for providing buoyancy, but as a means of protecting against the diving-related condition known as "the bends," which occurs when nitrogen in the blood bubbles as the diver rises to the surface. Helium is mixed with oxygen in diver's air tanks because it does not dissolve in the blood as easily as nitrogen. Among the most fascinating applications of helium relate to its extraordinarily low freezing point.

Helium has played a significant role in the low-temperature science known as cryogenics, and has found application in research concerning superconductivity: the use of very low temperatures to develop materials that conduct electrical power with vastly greater efficiency than ordinary conductors. Close to absolute zero, helium transforms into a highly unusual liquid unlike any known substance, in that it has no measurable resistance to flow. This means that it could carry an electrical current hundreds of times more efficiently than a copper wire. WHERE TO LEARN MORE "The Chemistry of the Rare Gases" (Web site). < (May 13, 2001). "Homework: Science: Chemistry: Gases" Channelone.com (Web site). < (May 12, 2001). Knapp, Brian J.; David Woodroffe; David A. Hardy. Elements. Danbury, CT: Grolier Educational, 2000. Mebane, Robert C. and Thomas R. Rybolt. Air and Other Gases. Illustrations by Anni Matsick. New York : Twenty-First Century Books, 1995. "Noble Gases" Xrefer.com (Web site).

< (May 13, 2001). Rare Gases. Praxair (Web site). < (May 13, 2001). Stwertka, Albert. Superconductors: The Irresistible Future. New York: F. Watts, 1991. Taylor, Ron. Facts on Radon and Asbestos. Illustrated by Ian Moores. New York: F. Watts, 1990. Cite this article Pick a style below, and copy the text for your bibliography. MLA Chemical Elements.com - Radon (Rn) Note: The external links below are not a part of this site and their content is not the responsibility of this site From The U.S. Environmental Protection Agency If you know of any other links for Radon, please let me know Bentor, Yinon. Chemical Element.com - Radon. < For more information about citing online sources, please visit the MLA's Website . This page was created by Yinon Bentor. Use of this web site is restricted by this site's license agreement . Copyright © 1996-2012 Yinon Bentor. All Rights Reserved.

Question: Which of the noble gases has the highest atomic number (86)?
Answer: Radon